'Odd Tic Tac' printed from http://nrich.maths.org/

Odd Tic Tac is another game for two players similar to Tic Tac
Toe. Find out if the strategies for play are the same. Using a 3 by
3 grid, one player writes O's and the other 1's taking it in turns.
To win you have to complete a line with an odd total.